The present invention relates to structures of headlamps for vehicles having a front lens, a light source, and a reflector for reflecting light incident from the light source in a direction toward the front lens, the front lens being slanted with respect to a vertical direction of a vehicle body.
A Japanese Patent Utility Model Application First Publication (Zikkai) Sho No. 54-47282 exemplifies such structure of the headlamp for vehicles.
In the above-identified Japanese Patent Utility Model Application Publication, the reflector includes a first light-reflecting surface like a substantially paraboloid of revolution at a center part thereof and a second light-reflecting surface at a peripheral portion on which flat stepwise portions and paraboloid of revolution surface having mutually different focal distances are alternatingly continued.
When some parts of the light beams from the light source fall on the center part of the reflector, they are reflected substantially in parallel to an optical axis of the light source.
On the other hand, when other parts of the light beams fall on the peripheral portion of the reflector, they become diffused and incident on the front lens which is vertical with respect to an elongated direction of a vehicle body.
To reduce the air resistance of a front surface of the vehicle body, so-called slant-type headlamps, in which the front lens is slanted with respect to the front surface of the vehicle body, are currently available on the market.
However, if the headlamp structure for vehicles disclosed in the above-identified Japanese Utility Model Application Publication is applied to the slant-type headlamp having the front lens directed upwardly with respect to the elongated direction of the vehicle body without alternation, an illumination pattern (so-called light distribution pattern) is distorted in such a form that both ends of the distribution pattern in a horizontal axial (H) direction droops with respect to an actual desirable light distribution pattern. This is best understood with reference to broken lines shown in FIG. 6, FIG. 8, FIG. 14, and FIG. 15, as compared with the actual desirable distribution pattern as denoted by solid lines in these drawings.
Consequently, it is not sufficient for the above-described structures of headlamps to visibly illuminate a left-side mark remotely located to the side of a vehicle running road, a left-side pedestrian and right-side pedestrian both walking beside the road as in the case of a road light distribution pattern i.e., the surface light distribution pattern at the time when an opposing vehicle passes aside the vehicle in a so-called asymmetrical passing beam mode. It is noted that another road surface light distribution pattern caused by another headlamp structure in which the front lens is vertically extended with respect to the elongated direction of the vehicle body can sufficiently illuminate the same left-side mark, left-side pedestrian, and right-side pedestrian thus ensuring safety driving of the vehicle.
On the other hand, in a case where the headlamp is one in which the front lens are directed downwardly, both ends of the light distribution pattern in the horizontal axial direction, in turn, rise and therefore the light irradiation by means of the headlamp structure described above in the right side direction in a country where traffic keeps to the left or on the left side in the case of U.S. may glare on the opposing vehicles passing to one side of the vehicle.